Suppose you want to test the effectiveness of a certain drug for treating a disease—that is, you want to see if using the drug is better the standard treatment. You select 150 patients to give the drug, and 150 patients to give the standard
treatment Name at least five factors you should control for in your samples to make the test more random

sorry but whats the question?

the purpose of the heading in the passage is to identify who is telling the story.

this excerpt is part of the book sugar changed the world (2010) written by marc aronson and marina budhos. as the book has been written by two people, the heading "marc" indicates that this specific excerpt is being narrated by aronson. in the fragment, marc describes his grandfather's story after hearing it from his cousin. however, there are other excerpts where budhos is the one that tells the story of her family.

aronson and budhos, who are husband and wife in real life, decided to write sugar changed the world when they found out how sugar, which had an important role in slavery and economy, changed their ancestors' lives.

you didn't show the passage, so unfortunately i cant you.